The first exercise to check alignment is to keep the feet forward. One way to do this is to find a straight edge, like on the sidewalk.
Feet forward, using sidewalk crack to check alignment
It may feel like your feet are pigeon-toed and your knees may want to fall in, but this demonstrates that the deep lateral rotators of your pelvis are weak and you need to rotate your femurs (thigh bones) out. It's a very subtle movement, and sometimes you can feel your arches lift when you do it correctly.
The movement doesn't come from your quadriceps, so make sure you can relax your kneecaps. If your kneecaps are pulled up, your quadriceps muscle is too tight and will pull your patellas into the space behind them, causing inflammation and irritation of the joint. You can practice lifting and lowering your kneecaps as you stand.
Now that your feet are forward and thighs externally rotated (rotated out), place your feet pelvis (not hip) width apart so your leg bones are vertical and keep your weight back on your heels, just enough to lift your toes so your ankles, knees, hips, shoulders, and ears are in a plumb line. Practice those few things to build your strong foundation. Please don't be discouraged. These habits take some time to break—it's like training a puppy. Stay on top of it; you won't be disappointed.
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